The World Trade Center ship "would have traveled up and down the river bringing cargo and people from the city to areas up north and might have gone as far south as the Caribbean."

Others have also suggested that the ship—which was likely deliberately sunk—may have done duty as a British troop carrier during the Revolutionary War.

—Brian Handwerk

Photograph by Lucas Jackson, Reuters

Bow Discovery at Ground Zero

A person touches a piece of the 50-foot-long (15-meter-long) World Trade Center ship's bow, found in July 2011.

The stern had been uncovered some 25 feet (8 meters) below street level in July 2010. Scientists quickly saw that its hull had been sliced in half.

They believed the ship's bow, if it still existed, would be on the other side of a 60-foot-tall (18-meter-tall) slurry wall, which stretches from the surface to the bedrock below—a theory that proved correct. Slurry walls allow for the building of tunnels or foundations in areas of soft earth that are close to open water or have a high groundwater table.

Fragments of decorative tiles (pictured) are among the many artifacts found near the ship at the 9/11 site. Perhaps unassociated with the vessel, the shards may have been dumped in the river at a time when the city was literally growing.

The ship itself was likely scrapped and sunk as part of the project to fill in the river and extend the city, Pappalardo explained.

Even before it was submerged, the boat was in bad shape. The wood shows damage from worms likely picked up in the Caribbean, while the upper deck and other presumably sound parts of the structure appear to have been stripped away before the ship was sunk, he said.

The buildings that stood here before 9/11 had relatively shallow basements, which didn't encroach on the buried ship and artifacts, even as surrounding properties were long ago excavated down to solid bedrock.

"It's unheard of to get this kind of opportunity to see an entire city block or two excavated to this depth," Meade said.

"It's really an amazing experience for us, and the last time a ship was found in the city was 1982—so it doesn't happen very often."